Method and apparatus for selecting network and distributing traffic in heterogeneous communication environment

ABSTRACT

According to an embodiment, a method for selecting an access network at user equipment in a mobile communication system includes step of receiving, from a base station, first setting information, and step of selecting the access network based on second setting information if the second setting information is received from the base station, or selecting the access network based on the first setting information if no second setting information is received. Using the proposed method, the user equipment can reduce user&#39;s inconvenience and save battery by blocking unnecessary offloading and wireless LAN scanning, and also can improve the quality of use and immediately respond to a cell change by preventing a ping-pong phenomenon.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 14/760,588, filed on Jul. 13, 2015 which claimed the benefit under35.U.S.C. §371 of an International application filed on Aug. 4, 2014 andassigned application number PCT/KR2014/007169, which claims the benefitof a Korean patent application filed on Aug. 2, 2013 in the KoreanIntellectual Property Office and assigned the serial number10-2013-0092156, the entire disclosure of each of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a wireless communication system andalso relates to a method and apparatus for a network selection andtraffic distribution in a heterogeneous communication environment. Moreparticularly, the present invention relates to a method for selecting anetwork depending on a moving velocity at user equipment (UE) and amethod for preventing a ping-pong phenomenon when the UE receivesoffload related message from a base station in 3GPP (The 3rd GenerationPartnership Project) system, e.g., UMTS (Universal MobileTelecommunications System), LTE (Long Term Evolution) system, etc.,interworking with a wireless LAN (WLAN).

2. Description of Related Art

Recently wireless communication technologies have made great advancesand thus communication system technologies have also evolvedcontinuously. Among them, UMTS system is one of the 3-generation mobilecommunication technologies, and LTE system is getting the spotlight asthe 4-generation mobile communication technology.

Additionally, the popularization of smart phones invites an explodinguse of data, and mobile communication network operators are now tryingto distribute users' data by combining WLAN network with the existingcellular network (i.e., 3G or 4G network) in order to cope with anexplosion in data.

However, in case of blindly offloading UE staying in cellular network toWLAN network, rapid degradation in quality felt by a user may be caused.For example, if UE which is moving at a high speed passes near a WLANaccess point (AP) and accesses it, the WLAN connection is cut offshortly and this causes inconvenience to a user. Further, since UEcontinuously discovers available WLAN in the neighborhood, a battery ofUE may be consumed rapidly.

In addition, after moving to WLAN network, UE does not know a state ofcellular network. Therefore, a solution for preventing UE from returningto cellular network at random is required.

SUMMARY OF THE INVENTION Technical Problem

Embodiments disclosed herein are proposed to solve the above-discussedissues, and the present invention provides a solution for a networkselection depending on a moving velocity at UE in case a cellularnetwork (e.g., 3G network such as UMTS, 4G network such as LTE, etc.)interworks with a WLAN network (i.e., short range communicationtechnology based on IEEE 802.11) in a wireless communication system, anda solution for returning to the cellular network when the UE receives aWLAN offload related message from a cellular base station.

Technical Solution

According to an embodiment disclosed herein, a method for selecting anaccess network at user equipment in a mobile communication systemincludes steps of receiving, from a base station, first settinginformation; and selecting the access network based on second settinginformation if the second setting information is received from the basestation, or selecting the access network based on the first settinginformation if no second setting information is received.

According to another embodiment disclosed herein, a method forsupporting a selection of an access network by user equipment at a basestation in a mobile communication system includes steps of transmittingfirst setting information to the user equipment; and transmitting secondsetting information to the user equipment, wherein the user equipmentselects the access network based on the second setting information ifthe second setting information is received, or selects the accessnetwork based on the first setting information if no second settinginformation is received.

According to still another embodiment disclosed herein, user equipmentfor selecting an access network in a mobile communication systemincludes a transceiver unit configured to transmit or receive a signalto or from a base station; and a control unit configured to control thetransceiver unit, to receive first setting information from the basestation, to select the access network based on second settinginformation if the second setting information is received from the basestation, or to select the access network based on the first settinginformation if no second setting information is received.

According to yet another embodiment disclosed herein, a base station forsupporting a selection of an access network by user equipment in amobile communication system includes a transceiver unit configured totransmit or receive a signal to or from the user equipment; and acontrol unit configured to control the transceiver unit, to transmitfirst setting information to the user equipment, and to transmit secondsetting information to the user equipment, wherein the user equipmentselects the access network based on the second setting information ifthe second setting information is received, or selects the accessnetwork based on the first setting information if no second settinginformation is received.

Advantageous Effects

By using the proposed method, the user equipment can reduce user'sinconvenience and save battery by blocking unnecessary offloading andwireless LAN scanning, and also can improve the quality of use andimmediately respond to a cell change by preventing a ping-pongphenomenon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a structure of LTE system in accordancewith an embodiment of this disclosure.

FIG. 2 is a diagram illustrating a wireless protocol structure in LTEsystem in accordance with an embodiment of this disclosure.

FIG. 3 is a diagram illustrating the first scenario of networkinterworking between 3GPP network and WLAN network in accordance with anembodiment of this disclosure.

FIG. 4 is a diagram illustrating a message flow regarding a scheme ofperforming access to WLAN network depending on a moving velocity of userequipment in accordance with an embodiment of this disclosure.

FIG. 5 is a diagram illustrating an example of an ANDSF policy includinga moving velocity of user equipment in accordance with an embodiment ofthis disclosure.

FIG. 6 is a diagram illustrating an operating process of user equipmentregarding a scheme of performing access to WLAN network depending on amoving velocity of user equipment in accordance with an embodiment ofthis disclosure.

FIG. 7 is a diagram illustrating the second scenario of networkinterworking between 3GPP network and WLAN network in accordance with anembodiment of this disclosure.

FIG. 8 is a diagram illustrating a message flow regarding a scheme ofoffloading specific user equipment only to WLAN network in accordancewith the first embodiment of this disclosure.

FIG. 9 is a diagram illustrating a message flow regarding a scheme ofoffloading specific user equipment only to WLAN network in accordancewith the second embodiment of this disclosure.

FIG. 10 is a diagram illustrating an operating process of user equipmentregarding a scheme of offloading specific user equipment only to WLANnetwork in accordance with the first embodiment of this disclosure.

FIG. 11 is a diagram illustrating an operating process of user equipmentregarding a scheme of offloading specific user equipment only to WLANnetwork in accordance with the second embodiment of this disclosure.

FIG. 12 is a block diagram illustrating a configuration of userequipment in accordance with an embodiment of this disclosure.

FIG. 13 is a block diagram illustrating a configuration of a basestation in accordance with an embodiment of this disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the present disclosure will be described with reference tothe accompanying drawings.

This disclosure may be embodied in many different forms and should notbe construed as limited to the embodiments set forth herein. Rather, thedisclosed embodiments are provided so that this disclosure will bethorough and complete, and will fully convey the scope of the inventionto those skilled in the art. The principles and features of thisinvention may be employed in varied and numerous embodiments withoutdeparting from the scope of the invention.

Furthermore, well known or widely used techniques, elements, structures,and processes may not be described or illustrated in detail to avoidobscuring the essence of the present invention. Although the drawingsrepresent exemplary embodiments of the invention, the drawings are notnecessarily to scale and certain features may be exaggerated or omittedin order to better illustrate and explain the present invention.

It will be understood that each block of the flowchart illustrations,and combinations of blocks in the flowchart illustrations, can beimplemented by computer program instructions. These computer programinstructions can be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which are executed via the processor of the computer or otherprogrammable data processing apparatus, create means for implementingthe functions specified in the flowchart block or blocks. These computerprogram instructions may also be stored in a computer usable orcomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer usable orcomputer-readable memory produce an article of manufacture includinginstruction means that implement the function specified in the flowchartblock or blocks. The computer program instructions may also be loadedonto a computer or other programmable data processing apparatus to causea series of operational steps to be performed on the computer or otherprogrammable apparatus to produce a computer implemented process suchthat the instructions that are executed on the computer or otherprogrammable apparatus provide steps for implementing the functionsspecified in the flowchart block or blocks.

And each block of the flowchart illustrations may represent a module,segment, or portion of code, which comprises one or more executableinstructions for implementing the specified logical function(s). Itshould also be noted that in some alternative implementations, thefunctions noted in the blocks may occur out of the order. For example,two blocks shown in succession may in fact be executed substantiallyconcurrently or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved.

The term “unit”, as used herein, may refer to a software or hardwarecomponent or device, such as a Field Programmable Gate Array (FPGA) orApplication Specific Integrated Circuit (ASIC), which performs certaintasks. A unit may be configured to reside on an addressable storagemedium and configured to execute on one or more processors. Thus, amodule or unit may include, by way of example, components, such assoftware components, object-oriented software components, classcomponents and task components, processes, functions, attributes,procedures, subroutines, segments of program code, drivers, firmware,microcode, circuitry, data, databases, data structures, tables, arrays,and variables. The functionality provided for in the components andmodules/units may be combined into fewer components and modules/units orfurther separated into additional components and modules.

Embodiments disclosed herein propose a method for restricting a networkselection depending on a moving velocity at user equipment and a methodfor preventing a ping-pong phenomenon after the user equipment receivesoffload related message from a base station in case a mobilecommunication network (e.g., UMTS, LTE, etc.) interworks with a WLANnetwork in a wireless communication system. Through this invention, theuser equipment can reduce user's inconvenience and save battery byblocking unnecessary offloading and WLAN scanning, and also can improvethe quality of use and immediately respond to a cell change bypreventing a ping-pong phenomenon.

Now, various embodiments of the present invention will be described withreference to the accompanying drawings.

According to an embodiment of this disclosure, the following scheme maybe proposed in order to prevent the transfer of user equipment (UE),moving at a high speed, to WLAN.

In case UE supports an access network discovery and selection function(ANDSF), the UE receives an ANDSF policy proposed in this invention froman ANDSF server, determines whether to perform a WLAN network discovery(or scanning), and performs a network selection.

-   -   Depending on a policy value, UE performs no WLAN network        discovery before selecting WLAN network, thus allowing a        reduction in battery.

According to another embodiment of this disclosure, in case UE receivesa message related to the transfer from ENB of cellular network to WLANnetwork, the following scheme may be proposed in order to prevent aping-pong phenomenon that indicates a return to the WLAN network.

-   -   When a message related to the transfer to WLAN network is        received from ENB of cellular network, a timer capable of        determining the validity of the received message is started.    -   The timer may be defined as a fixed value in the specification        or set by a message of a radio resource control (RRC) layer.    -   When UE moves to other cellular network or WLAN network during        the operation of the timer, the following embodiment may be        performed.    -   UE terminates the timer and determines again whether to perform        the access to cellular network.    -   UE terminates the timer and reports a change in an access state        of the UE to cellular network. Through the transmission of a        reporting message, the UE may receive a command of an access        return to cellular network from ENB.

UE may receive a command to maintain access with WLAN network fromcellular network during the operation of the timer.

-   -   When such a command to maintain access with WLAN is received, UE        resets the timer and performs a restart.    -   UE may receive a command to return to cellular network during        the operation of the timer.

When such a command to return to cellular network, UE terminates thetimer and tries to return to cellular network.

Although this invention is described by focusing on LTE system as oneexample of cellular network, it may be commonly applied to othercellular network (e.g., UMTS).

FIG. 1 is a diagram illustrating a structure of LTE system in accordancewith an embodiment of this disclosure.

Referring to FIG. 1, as shown, a wireless access network of LTE systemis formed of evolved node B (ENB, also referred to as node B or a basestation) 105, 110, 115 and 120, a mobility management entity (MME) 125,and a serving-gateway (S-GW) 130. User equipment (UE, also referred toas a terminal or a user device) 135 accesses an external network throughthe ENB 105˜120 and the S-GW 130.

The ENB 105˜120 of FIG. 1 corresponds to typical node B of UMTS system.The ENB is connected with the UE 135 through a wireless channel andperforms a more complicated role than typical node B. Since all usertraffics including a real-time service such as a voice over internetprotocol (VoIP) is serviced through a shared channel in LTE system, anapparatus that performs scheduling by collecting a buffer state of theUE, available transmission power state, a channel status, and the likeis required. This is performed by the ENB 105˜120. Normally one ENBcontrols a plurality of cells. For example, in order to realize atransmission speed of 100 Mbps, LTE system uses orthogonal frequencydivision multiplexing (OFDM) as wireless access technique at a bandwidthof 20 MHz. Also applied is an adaptive modulation and coding (AMC)scheme for determining a modulation scheme and a channel coding rateaccording to a channel status of the UE. The S-GW 130 is an apparatusfor offering data bearer and creates or removes data bearer under thecontrol of the MME 125. The MME is an apparatus for performing amobility management function for the UE and various control functionsand is connected with a plurality of ENBs.

FIG. 2 is a diagram illustrating a wireless protocol structure in LTEsystem in accordance with an embodiment of this disclosure.

Referring to FIG. 2, in each of UE and ENB, a wireless protocol of LTEsystem is formed of a packet data convergence protocol (PDCP) 205 or240, and a radio link control (RLC) 210 or 235, a medium access control(MAC) 215 or 230. The PDCP 205 or 240 performs IP headercompression/decompression, and the RLC 210 or 235 reconfigures a packetdata unit (PDU) with a suitable size. The MAC 215 or 230 is connectedwith various RLC layer devices formed in single UE and performs anoperation of multiplexing RLC PDUs to MAC PDU and demultiplexing RLCPDUs from MAC PDU. A physical layer 220 or 225 creates OFDM symbols bychannel-coding and modulating upper layer data and then transmits themto a wireless channel, or demodulates and channel-decodes OFDM symbolsreceived through a wireless channel and then transfers them to an upperlayer. Also, the physical layer uses hybrid ARQ (HARQ) for additionalerror correction, and a receiving end sends one bit indicating whetherpacket transmitted by a transmitting end is received or not. This isreferred to as HARQ ACK/NACK information. Downlink HARQ ACK/NACKinformation regarding uplink transmission may be transmitted through aphysical hybrid-ARQ indicator channel (PHICH), and uplink HARQ ACK/NACKinformation regarding downlink transmission may be transmitted through aphysical uplink control channel (PUCCH) or a physical uplink sharedchannel (PUSCH).

FIG. 3 is a diagram illustrating the first scenario of networkinterworking between 3GPP network and WLAN network in accordance with anembodiment of this disclosure.

Referring to FIG. 3, in this scenario, UE 315 receives ANDSF policies325 from an ANDSF server 317 and then selects an access network (i.e.,3GPP network and/or WLAN network).

The ANDSF policies 325 may include a policy to select only one of 3GPPnetwork and WLAN network, and may include a policy to simultaneouslyaccess both 3GPP network and WLAN network. For example, according to apolicy in case the UE 315 uses a voice over internet protocol (VoIP)service, VoIP packets are always offered through 3GPP network for aseamless service and the other internet packets may be offered through3GPP network or WLAN network selected depending on circumstances.

The ANDSF policies 325 may have therein various conditions for selectingWLAN network and 3GPP network. For example, a selection of WLAN networkmay be restricted to an AP having a low load of WLAN.

For example, if the ANDSF policies 325 include a policy instructing thata WLAN AP having channel utilization of 50% or under has a higher accesspriority than that of 3GPP network, UE 315 finds a certain AP 313through the discovery in neighboring WLAN network, receives the channelutilization of AP from the found AP 313 as indicated by a referencenumber 323, determines whether the condition is satisfied, and thendetermines whether to access the found AP.

In addition, if the ANDSF policies 325 include a policy instructing thatin case 3GPP network has a high load, a WLAN AP having channelutilization of 50% or under has a higher access priority than that of3GPP network, the UE 315 may receive load information 321 from the ENB311 of 3GPP network, determine whether the condition is satisfied, andthen determine whether to access the found AP. Such load information(RAN load) of 3GPP network may be transmitted via broadcast or unicast.In case of unicast transmission, this may be effective in forcingspecific UE to offload. In case both broadcast and unicast are usedtogether, if broadcast information indicates that a current load statusis normal, and if unicast information tells specific UE that a currentload status is high, the specific UE may try to access WLAN networkaccording to the above condition.

In embodiments of this disclosure, any condition associated with amoving velocity of UE may be added as an additional condition to be usedfor selecting WLAN network and 3GPP network in the ANDSF policies 325.Namely, for example, if there is a condition associated with a movingvelocity of the UE in the ANDSF policies 325, the UE 315 determineswhether a current moving velocity is smaller than the condition, andthen, in this case only, searches neighboring WLAN network. If any WLANAP satisfying the condition is found, the UE 315 tries to access thefound AP 313.

FIG. 4 is a diagram illustrating a message flow regarding a scheme ofperforming access to WLAN network depending on a moving velocity of userequipment in accordance with an embodiment of this disclosure.

Referring to FIG. 4, at step 411, UE 401 performs a procedure for accessto ENB 405 of 3GPP network and enters a state capable of transmitting orreceiving data to or from 3GPP network.

Thereafter, at step 413, the UE 401 can transmit or receive data to orfrom 3GPP network through the ENB 405.

Meanwhile, in case there is an ANDSF function in the network, the UE 401may transmit a message of requesting ANDSF related policies to an ANDSFserver 407 at step 415. Then, at step 417, the ANDSF server 407 maytransmit an ANDSF policy to the UE 401. Alternatively, in someembodiments, the ANDSF server 407 may transmit such an ANDSF policy tothe UE 401 without a request of the UE 401.

If there is no ANDSF function in the network, there may be apreconfigured ANDSF policy in the UE 401 as shown at step 419.

This ANDSF policy may include UE mobility information proposed inembodiments of this disclosure. Examples of such mobility informationare as follows.

-   -   Mobility State Estimation (MSE): A mobility state may be        determined as normal/medium/high according to the count of        handover/cell reselection of UE during a given time period        (T_(C)Rmax). For example, an MSE value of UE is not more        than/under normal, not more than/under medium, or not more        than/under high.    -   If the count of handover/cell reselection of UE during a given        time period exceeds N_(CR) _(—) _(H), mobility is regarded as        ‘high’.    -   If the count of handover/cell reselection of UE during a given        time period exceeds N_(CR) _(—) _(M) and fails to exceed N_(CR)        _(—) _(H), mobility is regarded as ‘medium’.    -   In the other case, mobility is regarded as ‘normal’.    -   Moving Velocity Value of UE: A moving velocity of UE (e.g., not        more than/under×km/h) is measured using GPS or the like.

The above-mentioned MSE information or moving velocity value may befurther contained, in the form as shown in FIG. 5, in the ANDSF policydefined in 3GPP standard 24.312. FIG. 5 is a diagram illustrating anexample of an ANDSF policy including a moving velocity of user equipmentin accordance with an embodiment of this disclosure. Referring to FIG.5, if a mobility value 501 is contained in the ANDSF policy, at leastone of an MSE value 503 and a moving velocity value 505 may becontained.

In case the mobility value 501 is contained, at step 421, the UE 401 maydetermine whether a current moving velocity of the UE 401 is not morethan/under the received information.

If a current moving velocity of the UE 401 is above or not less than thereceived policy value at step 423, the UE 401 may not access WLAN atstep 425 due to a strong possibility of disconnection in case of accessto WLAN. Additionally, in an embodiment, the UE 401 may maintain anaccess state with cellular network without discovering available WLANAPs 403.

However, if a current moving velocity of the UE 401 is not more than orunder the received policy value at step 431, the UE 401 starts adiscovery of the neighboring WLAN APs 403 at step 433 so as to determinewhether there is an available WLAN AP 403 in the neighborhood. Discoverytechniques for WLAN AP 403 may be a passive scanning technique and anactive scanning technique, as follows.

-   -   Passive Scanning Technique: UE receives all messages from        respective WLAN operating channels and then obtains beacon        messages transmitted by neighboring WLAN APs. In this manner,        neighboring WLAN APs can be found.    -   Active Scanning Technique: UE sends, to respective WLAN        operating channels, a probe request message inquiring about the        existence of neighboring WLAN APs and then receives a probe        response message. In this manner, neighboring WLAN APs can be        found.

When a WLAN signal (i.e., the above-mentioned beacon message or proberesponse message) is received from the WLAN AP 403 at step 435 using thepassive or active scanning technique, the UE 401 performs a procedurefor WLAN access to the AP 403 at step 437 and then transmits or receivesdata through the WLAN AP 403 at step 439.

FIG. 6 is a diagram illustrating an operating process of user equipmentregarding a scheme of performing access to WLAN network depending on amoving velocity of user equipment in accordance with an embodiment ofthis disclosure.

Referring to FIG. 6, at step 603, UE performs a procedure for access toENB of 3GPP network and enters a state capable of transmitting orreceiving data to or from 3GPP network. Thereafter, at step 605, the UEcan transmit or receive data to or from 3GPP network through the ENB.

Meanwhile, at step 607, the UE determines whether there is an ANDSFserver in 3GPP network. At this step, the UE may check whetherinformation associated with the ANDSF server is stored therein inadvance.

In case there is an ANDSF function in the network, the UE may transmit amessage of requesting ANDSF related policies to the ANDSF server at step611. Then, at step 613, the UE may receive an ANDSF policy from theANDSF server. Meanwhile, in an embodiment disclosed herein, the ANDSFpolicy may include a policy associated with UE mobility.

If there is no ANDSF function in the network, the UE determines at step609 whether any policy having preconfigured mobility information isstored therein. If there is no policy, the UE ends this process at step627.

If the UE receives an ANDSF policy from the ANDSF server or if the UEhas therein a preconfigured ANDSF policy, the UE determines at step 615whether a current moving velocity of the UE satisfies a moving velocitycontained in the ANDSF policy.

If a current moving velocity of the UE is not more than or under thereceived policy value, the UE 401 starts a discovery of neighboring WLANAPs at step 617 so as to determine whether there is an available WLAN APin the neighborhood. Discovery techniques for WLAN AP may be a passivescanning technique and an active scanning technique, as follows.

-   -   Passive Scanning Technique: UE receives all messages from        respective WLAN operating channels and then obtains beacon        messages transmitted by neighboring WLAN APs. In this manner,        neighboring WLAN APs can be found.    -   Active Scanning Technique: UE sends, to respective WLAN        operating channels, a probe request message inquiring about the        existence of neighboring WLAN APs and then receives a probe        response message. In this manner, neighboring WLAN APs can be        found.

At step 619, using the above-mentioned passive or active scanningtechnique, the UE determines whether any WLAN AP satisfying thecondition is found. If such a WLAN AP is found, the UE performs aprocedure for WLAN access to the AP at step 621 and then transmits orreceives data through the WLAN AP at step 623.

Thereafter, if it is not possible for the UE to maintain access to theWLAN AP at step 625 for reasons of lowering strength of a signal fromthe WLAN AP, the UE performs again a procedure for access to 3GPPnetwork at step 603 and then performs data transmission and receptionwith 3GPP network at step 605.

FIG. 7 is a diagram illustrating the second scenario of networkinterworking between 3GPP network and WLAN network in accordance with anembodiment of this disclosure.

Referring to FIG. 7, contrary to the FIG. 3 scenario for receiving anANDSF policy from the network and allowing UE to determine a networkselection, in this scenario the UE 715 collects (721) information aboutneighboring WLAN APs 713 and reports (723) it to ENB 711. Then the ENB711 determines a network selection and sends a command 725 to thespecific UE 715. When collecting WLAN AP information, the UE 715 maycollect information about signal strength and load of the neighboringWLAN AP 713 and transmit it to the ENB 711.

Meanwhile, in various scenarios as shown in FIGS. 3 and 7, the networkmay transmit a message related to WLAN offload to specific UE so as tomove such specific UE to WLAN rather than all UEs in a cell. Forexample, in case most traffic is formed by some specific UEs only fromamong UEs connected with the ENB 771, the WLAN offload of such UEs onlycan reduce significantly the load of cellular ENB. The followingdescription is applied to a case in which specific UEs are offloaded toWLAN in each scenario shown in FIGS. 3 and 7.

FIG. 8 is a diagram illustrating a message flow regarding a scheme ofoffloading specific user equipment only to WLAN network in accordancewith the first embodiment of this disclosure. This may be applied to theFIG. 3 scenario.

Referring to FIG. 8, at step 811, UE 801 performs a procedure for accessto ENB 805 of 3GPP network and enters a state capable of transmitting orreceiving data to or from 3GPP network.

Thereafter, at step 813, the UE 801 can transmit or receive data to orfrom 3GPP network through the ENB 805.

Meanwhile, in case there is an ANDSF function in the network, the UE 801may transmit a message of requesting ANDSF related policies to an ANDSFserver 807 at step 815. Then, at step 817, the ANDSF server 807 maytransmit an ANDSF policy to the UE 801.

Alternatively, the ANDSF server may transmit such an ANDSF policy to theUE without a request of the UE. If there is no ANDSF function in thenetwork, there may be a preconfigured ANDSF policy in the UE 801 asshown at step 819. In an embodiment, steps 815 and 817 may be performedoptionally.

An example of the ANDSF policy is as follows.

Example: In case UE accesses 3GPP network of operator A, and in casecurrent load information of ENB is ‘medium’ or more, increase accesspriority of a WLAN AP having a WLAN identifier ‘AAAA’.

Additionally, in an embodiment, it is possible to determine at least oneof an access network selection and a traffic steering policy on thebasis of information other than current load information of ENB. In thefollowing embodiment, information used for determining at least one ofan access network selection and a traffic steering policy may bereferred collectively to as load information of ENB.

As the above-mentioned WLAN identifier, a service set identifier (SSID)capable of being defined for each WLAN AP may be used.

Thereafter, at step 821 or 831, the UE 801 may receive signals ofneighboring WLAN APs 803 through a WLAN AP discovery. Discoverytechniques for WLAN APs may be a passive scanning technique and anactive scanning technique, as follows.

-   -   Passive Scanning Technique: UE receives all messages from        respective WLAN operating channels and then obtains beacon        messages transmitted by neighboring WLAN APs. In this manner,        neighboring WLAN APs can be found.    -   Active Scanning Technique: UE sends, to respective WLAN        operating channels, a probe request message inquiring about the        existence of neighboring WLAN APs and then receives a probe        response message. In this manner, neighboring WLAN APs can be        found.    -   Meanwhile, in case of a condition defining that current load        information of ENB is ‘medium’ or more, as shown in the above        example policy, each individual ENB 805 may transmit its own        current load information via broadcast at step 823 or via        unicast at step 825.

If the ENB 805 sends its own load information via broadcast at step 823,all UEs in a cell can receive and utilize a broadcast transmissionmessage. This example supposes that current load information of ENB istransmitted as ‘low’. According to an embodiment, the broadcasttransmission message may be sent through a system information block(SIB) message of the RRC layer. Also, in an embodiment, information usedfor ENB to determine at least one of an access network selection and atraffic steering policy may include at least one of WLAN channelutilization, a WLAN downlink backhaul rate, a WLAN uplink backhaul rate,a received channel power indicator (RCPI) of WLAN, a received signal tonoise indicator (RSNI) of WLAN, information associated with referencesignal receive power (RSRP) of ENB, and information associated withreference signal received quality of ENB. For example, it is possible todeliver information associated with a threshold value of one of theabove kinds of information and then, based on the threshold value,select an access network or perform a traffic steering. Specifically, ifmeasured information exceeds a threshold value as the result ofcomparison between information received from ENB by UE and informationmeasured by UE, it is possible to select, as an access network, at leastone of ENB and WLAN or perform a traffic steering.

Additionally, in an embodiment, the above-mentioned WLAN channelutilization may include load-related information of WLAN.

Meanwhile, in order for the ENB 805 to offload specific UE 801 only toWLAN at step 825, it may be supposed that a current load state of theENB is transmitted as ‘high’ to the UE 801 via unicast. According to anembodiment, this unicast message may be transmitted through a message ofthe RRC layer. This RRC layer message may include anRRCConnectionReconfiguration message. If the UE 801 receives both abroadcast transmission message and a unicast transmission message, theUE 801 may use the unicast message prior to the broadcast message.Namely, although the UE 801 receives low and high load states of the ENB805 in this example, the UE 801 may determine, based on the unicastmessage, that the load state of the ENB 805 is ‘high’. Specifically, ifthe UE receives both broadcast transmission information and unicasttransmission information and if the unicast transmission information isnot released, the UE may select an access network or perform a trafficsteering on the basis of the unicast transmission information. Also, incase the UE receives repeatedly such unicast information, the UE mayapply the latter-received information and release the former-receivedinformation.

Meanwhile, in order to determine whether information received viaunicast is valid, an embodiment may introduce a validity timer. When aunicast message is received, the UE 801 may determine that informationreceived via unicast is valid until the expiry of the validity timer.Additionally, after the expiry of the validity timer, the UE 801determines that information received via unicast is not valid any more.Also, in this case, the UE may discard information received via unicast.

Namely, at step 827, the UE 801 may start the timer. Then the UE 801 maydetermine that load information of dedicated signaling is valid untilthe expiry of the timer. Additionally, depending on embodiments, thetimer may be started at a time point when timer related information isreceived, when the UE 801 accesses the WLAN AP 803, or when the UEenters an RRC idle state.

Namely, at step 829, in case the validity timer runs, the UE 801recognizes that the load state of the ENB 805, received via unicast, is‘high’, and then determines access by determining whether there is anetwork having higher priority satisfying the above-mentioned ANDSFpolicy. If the timer expires, the UE 801 determines that the receivedinformation indicating a high load state of the ENB 805 is not valid anymore. In case there is information received via broadcast as shown inthis embodiment, the UE determines access at step 841 by determining,based on the received broadcast information, whether there is a networkhaving higher priority satisfying the above-mentioned ANDSF policy.Namely, the UE recognizes that the load state of the ENB 805 is ‘low’,and then determines access by determining whether there is a networkhaving higher priority satisfying the above-mentioned ANDSF policy.Meanwhile, contrary to this embodiment, if there is no broadcastinformation and there is only information received via unicast, and ifthe timer expires, the UE 801 may determine that there is no valid loadinformation of the ENB 805, and then determine access by determiningwhether there is a network having higher priority satisfying theabove-mentioned ANDSF policy.

If any WLAN network having higher access priority exists considering theANDSF policy from a value received through the unicast or broadcastmessage, the UE 801 receives signals from neighboring WLAN APs 803 byusing the above-mentioned passive or active scanning technique at step831. If there is a WLAN AP satisfying the condition, the UE 801 performsa procedure for WLAN access to such a WLAN AP at step 833. Then, at step835, the UE 801 may perform data transmission or reception with theaccessed WLAN AP 803.

In an embodiment, after a successful access with the WLAN AP 803, the UE801 does not perform data transmission and reception with 3GPP network.However, in order to receive an incoming call or the like, the UE 801may enter an idle state and periodically receive a paging message or thelike.

Meanwhile, for reasons of the movement of the UE 801 or the like, acertain case in which the UE 801 moves from the current ENB 805 of 3GPPnetwork to other ENB or in which the UE 801 changes access to other WLANAP 803 may be further considered.

If the UE 801 moves from the current ENB of 3GPP network to other ENB atstep 837, the UE 801 may have a possibility of using again a servicethrough 3GPP network since the latter ENB is different in load state andvolume from the former ENB.

Therefore, if the validity timer is running when the UE 801 moves fromthe current ENB of 3GPP network to other ENB or changes access to otherWLAN AP, at step 839 the UE 801 terminates the validity timer anddetermines that information received via unicast is not valid any more.Then the UE 801 determines access by determining again whether there isa network having higher priority satisfying the above-mentioned ANDSFpolicy. Through this method, the UE can determine promptly a network tobe accessed in case of a cell change, and this may improve usersatisfaction.

In an embodiment, a value related to the timer may be offered to the UE801 through one or more of steps 811 and 825. Alternatively, a valuepreconfigured in the UE 801 may be used. Such a value related to thetimer may include a time value of the timer.

FIG. 9 is a diagram illustrating a message flow regarding a scheme ofoffloading specific user equipment only to WLAN network in accordancewith the second embodiment of this disclosure. This may be applied tothe FIG. 7 scenario.

Referring to FIG. 9, at step 911, UE 901 performs a procedure for accessto ENB 905 of 3GPP network and enters a state capable of transmitting orreceiving data to or from 3GPP network. Thereafter, at step 913, the UE901 can transmit or receive data to or from 3GPP network through the ENB905.

Thereafter, at step 915, the UE 901 receives signals from neighboringWLAN APs 903 by using the above-mentioned passive or active scanningtechnique so as to check whether there is a suitable WLAN AP 903 foroffload in the neighborhood. This signal may be a beacon message or aprobe response message received from the WLAN AP 903.

If the UE 901 finds any WLAN AP suitable for offload, the UE 901 reportsrelevant information to the ENB 905 at step 917. A report message mayuse a MeasurementReport message of RRC layer and may contain one or moreof signal strength and load information of the WLAN AP 903. Such signalstrength and load information of the WLAN AP 903 may be obtained throughthe above-mentioned beacon message or probe response message.

At step 921, the ENB 905 that receives information about the neighboringWLAN AP 903 from the UE 901 may determine, based on the receivedinformation, whether to offload the UE 901 to the reported WLAN AP 903.Additionally, in some embodiments, the ENB 905 may determine whether tooffload the UE 901 to the reported WLAN AP 903, further considering oneor more of a current load state of the ENB 905 and the quantity oftraffic produced by the UE 901.

If it is determined to offload the UE 901 to the WLAN AP 903, the ENB905 transmits an offload command to one of the WLAN APs 903, or somecandidates thereof, reported to the UE 901 at step 923. In someembodiments, the offload command may use a message of RRC layer.

Meanwhile, when the UE 901 receives the offload command message from theENB 905, the UE 902 starts at step 925 a timer for determining whetherthe command is valid. A value related to the timer may be offered to theUE 901 at steps 923 and 911. This value may include a timer time value.Specifically, at step 921, the ENB 905 may determine a timer time value,based on the reported information, and then offer it to the UE 901.

If the validity timer expires, the UE 901 determines at step 941 thatthe offload command is not valid any more, and then tries to return to3GPP network.

At step 927, the UE 901 that receives the offload command messageperforms a WLAN access procedure to one of the WLAN APs 903 specified inthe command message.

Thereafter, in case of succeeding in the WLAN access procedure, the UE901 may perform data communication with the WLAN AP 903 at step 929.

Otherwise, in case of failing in the WLAN access procedure, the UE 901may perform again the WLAN access procedure to another AP specified inthe command message at step 927.

In case of all failures, the UE 901 terminates the validity timer andtries to return to 3GPP network at step 941.

Depending on embodiments, the ENB 905 may offer a message forinstructing a return to 3GPP network to the UE. This message may betransmitted through paging.

Meanwhile, for reasons of the movement of the UE 901 or the like, acertain case in which the UE 901 moves from the current ENB of 3GPPnetwork to other ENB or in which the UE 901 changes access to other WLANAP may be further considered.

If the UE 901 moves from the current ENB 905 of 3GPP network to otherENB 907 at step 931, the UE 901 may have a possibility of using again aservice through 3GPP network since the latter ENB 907 is different inload state and volume from the former ENB 905.

Therefore, at step 935, the UE 901 may report such changes to the newENB 907. Depending on embodiments, a report message may use a message ofRRC layer and contain therein one or more of a 3GPP network change stateand a WLAN AP change state (including signal strength and loadinformation of WLAN AP).

The new ENB 907 that receives the reported changes may determine againwhether to offload, and then, as discussed at step 923, transmit anoffload command or a message of command to return to 3GPP network to theUE 901.

Meanwhile, at step 937, the new ENB 907 may manage a state in which thespecific UE 901 is offloaded in WLAN, and may also transmit, to the UE901, a message of command to keep staying in WLAN such that the UE 901may not return to 3GPP network. If the UE 901 receives the commandmessage from the new ENB 907 and if the timer has already operated, theUE 901 restarts the validity timer to extend the timer at step 939.

FIG. 10 is a diagram illustrating an operating process of user equipmentregarding a scheme of offloading specific user equipment only to WLANnetwork in accordance with the first embodiment of this disclosure.

Referring to FIG. 10, at step 1003, UE performs a procedure for accessto ENB of 3GPP network and enters a state capable of transmitting orreceiving data to or from 3GPP network. Thereafter, at step 1004, the UEcan transmit or receive data to or from 3GPP network through the ENB.

Thereafter, at step 1005, the UE receives an ANDSF policy from thenetwork or checks a preconfigured ANDSF policy. Specifically, in casethere is an ANDSF function in the network, the UE may transmit a messageof requesting ANDSF related policies to an ANDSF server. Then the ANDSFserver may transmit an ANDSF policy to the UE. Alternatively, the ANDSFserver may transmit such an ANDSF policy to the UE without a request ofthe UE. If there is no ANDSF function in the network, there may be apreconfigured ANDSF policy in the UE.

An example of the ANDSF policy is as follows. Example: In case UEaccesses 3GPP network of operator A, and in case current loadinformation of ENB is ‘medium’ or more, increase access priority of aWLAN AP having a WLAN identifier ‘AAAA’.

The WLAN identifier may use SSID or the like.

Meanwhile, in case of a condition defining that current load informationof ENB is ‘medium’ or more, as shown in the above example policy, the UEmay receive current load information of the ENB via broadcast at step1007 or via unicast at step 1009.

If the UE receives the unicast load information at step 1009, the UEstarts the validity timer at step 1011. The timing of starting the timermay be started at a time point when timer related information isreceived, when the UE applies access technique according to the loadinformation, or when the UE enters an RRC idle state.

If the validity timer runs or if the UE receives load information viaunicast and is in an RRC CONNECTED state, the UE determines at step 1015that information received as the unicast message is valid, and alsodetermines an ANDSF policy by using the received information. Namely,when the UE determines whether to access which network (e.g., 3GPPnetwork or WLAN network), the UE selects a network satisfying the ANDSFpolicy by utilizing information received via unicast.

However, if the validity timer fails to run, the UE determines at step1017 that information received via unicast is not valid any more, andthen determines an ANDSF policy by using any information other than theinformation received via unicast. Namely, if there is informationreceived via broadcast, the UE utilizes this information. If there is noinformation received, the UE may perform the determination of ANDSFpolicy without any information received from the ENB.

Thereafter, if any WLAN network having higher access priority existsconsidering the ANDSF policy from a value received through the unicastor broadcast message at step 1019 or 1021, the UE receives signals fromneighboring WLAN APs by using the above-mentioned passive or activescanning technique. If there is a WLAN AP satisfying the condition, theUE performs a procedure for WLAN access to such a WLAN AP at step 1023.

Then, at step 1025, the UE may perform data transmission or receptionwith the accessed WLAN AP. After a successful access with the WLAN AP,the UE does not perform data transmission and reception with 3GPPnetwork. However, in order to receive an incoming call or the like, theUE may enter an idle state and periodically receive a paging message orthe like.

Meanwhile, for reasons of the movement of the UE or the like, a certaincase in which the UE moves from the current ENB of 3GPP network to otherENB or in which the UE changes access to other WLAN AP may be furtherconsidered.

If the UE moves from the current ENB of 3GPP network to other ENB, theUE may have a possibility of using again a service through 3GPP networksince the latter ENB is different in load state and volume from theformer ENB. Therefore, if the UE moves from the current ENB of 3GPPnetwork to other ENB, or if the UE changes access to other WLAN AP, orif the validity timer expires at step 1027, the UE terminates thevalidity timer at step 1017, determines that information received viaunicast is not valid any more, and then determines an ANDSF policy byusing any information other than the information received via unicast.Otherwise, the UE continuously determines at step 1029 whether it ispossible to maintain WLAN access. If not possible, the UE tries toreturn to 3GPP network at step 1003.

Through this method, the UE can determine promptly a network to beaccessed in case of a cell change, and this may improve usersatisfaction.

FIG. 11 is a diagram illustrating an operating process of user equipmentregarding a scheme of offloading specific user equipment only to WLANnetwork in accordance with the second embodiment of this disclosure.

Referring to FIG. 11, at step 1103, UE performs a procedure for accessto ENB of 3GPP network and enters a state capable of transmitting orreceiving data to or from 3GPP network. Thereafter, at step 1105, the UEcan transmit or receive data to or from 3GPP network through the ENB.

Thereafter, at step 1107, the UE performs a WLAN discovery so as to findneighboring WLAN APs.

If the UE finds any WLAN AP through the WLAN discovery procedure at step1109, the UE reports the found WLAN AP to the ENB at step 1111.

Thereafter, when the UE receives an offload command message from the ENBat step 1113, the UE performs a WLAN access procedure to the relevant APin response to the offload command at step 1115. If there is two or moreWLAN APs in the offload command message, the UE performs a WLAN APaccess procedure according to priorities specified in the message. If anaccess procedure to a certain WLAN AP fails, the UE tries to access inorder the other WLAN APs specified in the offload command message.

In case of succeeding in the WLAN AP access procedure, the UE starts thevalidity timer and performs data communication with the AP at step 1117.Thereafter, if the validity timer expires, the UE tries to return to3GPP network at step 1103. If the validity timer does not expire and aconnection maintenance command message is received from the ENB at step1121, the UE may restart the validity timer and also maintain datacommunication with the AP at step 1117. Meanwhile, if a message ofcommand to return to 3GPP network is received from the ENB at step 1123,the UE tries to access 3GPP network in response to this command at step1103.

Additionally, if a cell change in 3GPP network or a change between WLANAPs occurs at step 1125 while the UE accesses WLAN, the UE reports sucha change to the ENB at step 1127 such that the ENB can take a promptaction.

FIG. 12 is a block diagram illustrating a configuration of userequipment (UE) in accordance with an embodiment of this disclosure.

Referring to FIG. 12, the UE according to an embodiment of thisinvention includes a transceiver unit 1205, a control unit 1210, amultiplexer/demultiplexer unit 1215, a control message processing unit1230, and an upper layer processing unit 1220.

The transceiver unit 1205 receives data and control signals through aforward channel of a serving cell and transmits data and control signalsthrough a backward channel. In case a plurality of serving cells areset, the transceiver unit 1205 performs transmission and reception ofdata and control signals through the plurality of serving cells.

The multiplexer/demultiplexer unit 1215 multiplexes data generated atthe upper layer processing unit 1220 or the control message processingunit 1230, or demultiplexes data received at the transceiver unit 1205and then delivers them to the upper layer processing unit 1220 or thecontrol message processing unit 1230.

The control message processing unit 1230 processes a control messagereceived from ENB and then takes a suitable action. For example, ifDRX-related parameters are received, the control message processing unit1230 transfers these parameters to the control unit.

The upper layer processing unit 1220 may be configured for each service.The upper layer processing unit 1220 processes data generated in a userservice such as FTP (File Transfer Protocol) or VoIP (Voice overInternet Protocol) and then transfers them to themultiplexer/demultiplexer unit 1215, or processes data received from themultiplexer/demultiplexer unit 1215 and then transfers them to a serviceapplication on the upper layer.

The control unit 1210 checks a scheduling command, e.g., backwardgrants, received through the transceiver unit 1205 and thereby controlsthe transceiver unit 1205 and the multiplexer/demultiplexer unit 1215such that backward transmission can be performed with a suitabletransmission resource at a suitable time point. Also, the control unitcontrols the transceiver unit in connection with DRX operation andCSI/SRS transmission.

In this invention, the UE may further have a WLAN device 1245. In casethere is a need for a WLAN discovery according to a policy/commandreceived from the network or ENB, a WLAN discovery/selection instructingunit 1240, proposed in this invention, notifies the WLAN device 1245 toperform a discovery for neighboring WLAN APs.

FIG. 13 is a block diagram illustrating a configuration of a basestation (ENB) in accordance with an embodiment of this disclosure.

The ENB shown in FIG. 13 includes a transceiver unit 1305, a controlunit 1310, a multiplexer/demultiplexer unit 1320, a control messageprocessing unit 1335, various upper layer processing units 1325 and1330, and a scheduler 1315.

The transceiver unit 1305 transmits data and control signals through aforward carrier and receives data and control signals through a backwardcarrier. In case a plurality of carriers are set, the transceiver unit1305 performs transmission and reception of data and control signalsthrough the plurality of carriers.

The multiplexer/demultiplexer unit 1320 multiplexes data generated atthe upper layer processing units 1325 and 1330 or the control messageprocessing unit 1335, or demultiplexes data received at the transceiverunit 1305 and then delivers them to the upper layer processing units1325 and 1330, the control message processing unit 1335, or the controlunit 1310. The control message processing unit 1335 processes a controlmessage transmitted from UE and then takes a suitable action, or createsa control message to be transmitted to the UE and delivers it to thelower layer.

The upper layer processing units 1325 and 1330, which may be configuredfor each service, process data generated in a user service such as FTPor VoIP and then transfer them to the multiplexer/demultiplexer unit1320, or process data received from the multiplexer/demultiplexer unit1320 and then transfers them to a service application on the upperlayer.

The control unit 1310 determines when UE will transmit CSI/SRS, andthereby controls the transceiver unit.

The scheduler 1315 allocates transmission resources to UE at a suitabletime point by considering a buffer state of UE, a channel status, anactive time of UE, and the like, and thereby allows the transceiver unitto process signals received from UE or transmit signals to UE.

By using the proposed method, UE can reduce user's inconvenience andsave battery by blocking unnecessary offloading and WLAN scanning, andalso can improve the quality of use and immediately respond to a cellchange by preventing a ping-pong phenomenon.

While this invention has been particularly shown and described withreference to an exemplary embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of thisinvention as defined by the appended claims.

What is claimed is:
 1. A method of terminal in a communication system,the method comprising: receiving, from a base station, a systeminformation block including first radio access network (RAN) assistanceinformation; receiving, from the base station, radio resource control(RRC) connection reconfiguration message including second RAN assistanceinformation; identifying whether a timer associated with the second RANassistance information expires; and discarding the second RAN assistanceinformation and applying the first RAN assistance information, if thetimer associated with the second RAN assistance information expires. 2.The method of claim 1, further comprising: applying, if the timer is notexpired or stopped, the second RAN assistance information in the RRCconnection reconfiguration message.
 3. The method of claim 1, furthercomprising: identifying when cell reselection occurs while the timer isrunning; and stopping, when the cell reselection occurs while the timeris running, the timer.
 4. The method of claim 1, wherein the systeminformation block is broadcasted from the base station.
 5. The method ofclaim 1, further comprising: applying, if the second RAN assistanceinformation is not configured, the first RAN assistance information. 6.A terminal in a communication system, the terminal comprising: atransceiver configured to transmit and receive a signal; and acontroller is configured to: receive, from a base station, a systeminformation block including first radio access network (RAN) assistanceinformation; receive, from the base station, a radio resource control(RRC) connection reconfiguration message including second RAN assistanceinformation, identify whether a timer associated with the second RANassistance information expires, and discard the second RAN assistanceinformation and apply the first RAN assistance information, if the timerassociated with the second RAN assistance information expires.
 7. Theterminal of claim 6, wherein the controller is further configured to:apply, if the timer is not expired or stopped, the second RAN assistanceinformation in the RRC connection reconfiguration message.
 8. Theterminal of claim 6, wherein the controller is further configured to:identify when cell reselection occurs while the timer is running, andstop, if the cell reselection occurs while the timer is running, thetimer.
 9. The terminal of claim 6, wherein the system information blockis broadcasted from the base station.
 10. The terminal of claim 6,wherein the controller is further configured to: apply, if the secondRAN assistance information is not configured, the first RAN assistanceinformation.